There was a question recently about whether a Keyton on Ebay had A51 grinds or not. Apparently, there is some confusion about what “Area 51” grinds are, so I took a pic that should explain it.
L-R: Bead Blast Mini Keyton w/ no A51 grinds; Stonewashed Mini Keyton w/ partial A51 grinds; Stonewashed Mini Keyton w/ full A51 grinds.
These are all full thickness Keytons, no flats.
Hope this helps.